Madrid -LRB- CNN -RRB- -- It 's a check for $ 2 million , issued to a man with a California driver 's license . And it was found in a subway car in Madrid , police say .

`` We have his name . We 're trying to locate this person , '' a National Police spokesman in Madrid told CNN on Thursday .

`` We wo n't just hand it over . We have to verify that the origin of the money is not illicit , '' said the spokesman , who by custom is not identified .

The check was issued by Bank of America , and it 's post-dated to January 2014 , the spokesman said .

A maintenance worker for Madrid 's Metro , or subway system , found it Wednesday . A train running on line 5 , which roughly traverses the capital from east to west , reported a problem with doors that would n't fully close at the Diego de Leon station .

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The train was sent to a maintenance yard , following protocol , and a worker who inspected the doors found a brown leather wallet that contained the $ 2 million check , the California driver 's license and some credit cards , a Metro de Madrid spokeswoman said .

`` It appears that the wallet was stolen on the Metro , '' the spokeswoman said . `` The thief looked inside , grabbed the cash -- but did n't see the check -- and then threw the wallet away . ''

Usually , these kinds of discarded stolen wallets end up on a station platform . But this one landed in the doorway of a Metro car , preventing it from closing properly , she said .

Madrid 's Metro handles an average of 2 million passengers a day , but this is believed to be the first time that one of them was carrying a $ 2 million check , the police spokesman said .

Why would someone with such a large check be riding in the subway , instead of in a chauffeured car ?

Police would like to ask the owner of the check that question , too , the spokesman said .

Police have contacted the U.S. Embassy in Madrid for help in finding the check 's owner , but the embassy had no immediate comment .

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A maintenance worker for Madrid 's subway system found the check Wednesday

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It was in a wallet and made out to a man with a California driver 's license

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`` It appears that the wallet was stolen on the Metro , '' a subway system spokeswoman says

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`` We have to verify that the origin of the money is not illicit , '' a police spokesman says